L9959 - SPI Controlled 8-Channel Low-Side Driver | STMicroelectronics
MPN: L9959 ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.25 | $3.25 |
| 10 | $2.95 | $29.50 |
| 100 | $2.65 | $265.00 |
| 500 | $2.4 | $1,200.00 |
| 1,000 | $2.2 | $2,200.00 |
L9959 Overview
A low-side driver is a type of power switch that connects the load to ground when activated, allowing the load to be powered from a positive supply. In automotive systems, low-side drivers are commonly used to control lamps, relays, and actuators, where the load is connected between the battery positive and the driver output. The L9959 fits into the broader category of smart power switches, which integrate protection and diagnostic features to enhance system reliability. These devices are essential in modern vehicle body control modules, where multiple loads must be managed efficiently.
Key features of the L9959 include an SPI interface for serial control and readback of diagnostic information, a 40V load voltage rating, and a low quiescent current of 10 µA in standby mode. Each output can sink up to 1.2A, and the device includes overcurrent, overtemperature, and open-load detection for robust protection. The SPI interface operates at up to 5 MHz, enabling fast communication with microcontrollers. The PowerSO-20 package offers excellent thermal performance, with a thermal resistance of 35 °C/W, allowing operation at high ambient temperatures.
The L9959 is built using STMicroelectronics' BCD (Bipolar-CMOS-DMOS) technology, which combines low-power CMOS logic with high-voltage DMOS power stages. This architecture enables efficient switching and precise analog diagnostics. The device includes a 16-bit SPI register for configuration and status readback, allowing real-time monitoring of output states and fault conditions. The integrated protection features ensure safe operation under short-circuit and thermal stress, reducing the need for external components.
Typical applications include automotive body control modules, where the L9959 drives exterior and interior lighting, relays, and small motors. It is also used in industrial PLCs for controlling solenoids and valves, and in building automation for lighting control. The SPI interface simplifies wiring and reduces the number of microcontroller I/O pins required, making it a cost-effective solution for multi-channel switching.
When designing with the L9959, ensure proper decoupling of the VCC supply with a 100 nF ceramic capacitor placed close to the pin. The SPI lines should be kept short and shielded to minimize noise, and the ground plane should be solid to handle the return currents from multiple outputs. Thermal management is critical when driving high currents; use adequate copper area on the PCB to dissipate heat.
Drop-in alternatives for L9959 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
L9959TR
✅ Drop-In📋 Reference alternative (not in catalog)
L9958
⚡ Same Package ⚠️ Specs Unverified✓ In Stock
$6.2 / Unit
View Datasheet →MC33879
⚡ Same Package ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
L9959 Maximum Ratings & Electrical Characteristics
| Number of Channels | 8 |
| Output Type | Low-Side |
| Supply Voltage (VCC) | 4.5 V to 5.5 V |
| Load Voltage | 40 V (max) |
| Output Current per Channel | 1.2 A (continuous) |
| SPI Interface | Yes, up to 5 MHz |
| Quiescent Current | 10 µA (standby) |
| Overcurrent Protection | Yes |
| Overtemperature Protection | Yes |
| Open-Load Detection | Yes |
| Package | PowerSO-20 |
| Mounting Type | Surface Mount |
| Operating Temperature | -40°C to +150°C |
| Thermal Resistance, Junction-to-Ambient | 35 °C/W |
| RoHS Status | Compliant |
L9959 Pin Configuration
| Pin 1 | OUT1 — Low-side output channel 1 |
| Pin 2 | OUT2 — Low-side output channel 2 |
| Pin 3 | OUT3 — Low-side output channel 3 |
| Pin 4 | OUT4 — Low-side output channel 4 |
| Pin 5 | GND — Ground |
| Pin 6 | OUT5 — Low-side output channel 5 |
| Pin 7 | OUT6 — Low-side output channel 6 |
| Pin 8 | OUT7 — Low-side output channel 7 |
| Pin 9 | OUT8 — Low-side output channel 8 |
| Pin 10 | VCC — Logic supply voltage (4.5V to 5.5V) |
| Pin 11 | CSN — SPI chip select (active low) |
| Pin 12 | SCLK — SPI clock |
| Pin 13 | SDI — SPI data input |
| Pin 14 | SDO — SPI data output |
| Pin 15 | GND — Ground |
| Pin 16 | GND — Ground |
| Pin 17 | GND — Ground |
| Pin 18 | GND — Ground |
| Pin 19 | GND — Ground |
| Pin 20 | GND — Ground |
Typical Applications
L9959 is suitable for 6 applications: Automotive Body Control Module, Industrial PLC Output Module, Building Automation Lighting Control, LED Matrix Display Driver, Relay Driver for Home Automation, Medical Device Actuator Control.
Automotive Body Control Module
The L9959 is ideal for automotive body control modules, where it drives exterior and interior lighting, relays, and small motors. Its 8 channels allow control of multiple loads with a single SPI interface, reducing wiring complexity. The 40V load voltage rating handles automotive battery transients, and the integrated protection features ensure reliable operation in harsh environments. The low quiescent current of 10 µA helps minimize battery drain when the vehicle is off. The SPI interface enables real-time diagnostics, allowing the ECU to monitor load status and detect faults such as open circuits or short circuits. The PowerSO-20 package provides good thermal performance, essential for driving multiple loads simultaneously. Compared to discrete MOSFET solutions, the L9959 simplifies design and reduces component count, improving overall system reliability.
Recommended
Industrial PLC Output Module
In industrial PLCs, the L9959 is used to drive solenoids, valves, and indicator lamps. Its 8 channels allow a single device to control multiple outputs, saving PCB space and cost. The SPI interface simplifies communication with the PLC's microcontroller, and the open-load detection feature helps identify disconnected loads, improving system diagnostics. The wide operating temperature range of -40°C to +150°C ensures reliable operation in factory environments. The overcurrent protection prevents damage from short circuits, which is common in industrial wiring. The low-side driver configuration is suitable for loads connected to a positive supply, which is typical in 24V industrial systems. The L9959's high current capability of 1.2A per channel can drive most industrial solenoids and valves directly, eliminating the need for external drivers.
Recommended
Building Automation Lighting Control
The L9959 is well-suited for building automation systems, where it controls lighting circuits and small motors. Its 8 channels can switch multiple lighting zones, and the SPI interface allows centralized control from a building management system. The low quiescent current is beneficial for always-on systems, reducing energy consumption. The open-load detection can alert maintenance personnel to burnt-out lamps, enabling proactive replacement. The device's protection features ensure safe operation in commercial buildings, where electrical faults can be hazardous. The PowerSO-20 package is compact, fitting into standard control panels. The 40V load voltage rating is sufficient for 24V lighting systems commonly used in commercial buildings. The L9959's ability to drive both resistive and inductive loads makes it versatile for various lighting and motor applications.
Recommended
LED Matrix Display Driver
The L9959 can be used to drive LED matrix displays, where each channel controls a row or column of LEDs. Its 8 channels allow driving an 8x8 matrix with external multiplexing. The SPI interface enables fast updates, and the open-load detection can identify faulty LED strings. The overcurrent protection prevents damage from LED short circuits. The low-side driver configuration is suitable for common-anode LED matrices. The device's high current capability of 1.2A per channel can drive multiple LEDs in parallel, reducing the need for external transistors. The compact PowerSO-20 package is ideal for space-constrained display modules. The wide operating temperature range allows outdoor use. The L9959's diagnostic features enhance the reliability of LED displays, which are often used in advertising and information systems.
Recommended
Relay Driver for Home Automation
The L9959 is an excellent choice for home automation systems, where it drives relays for lighting, heating, and appliance control. Its 8 channels can control multiple relays, and the SPI interface allows integration with smart home hubs. The low quiescent current is important for energy-efficient systems. The open-load detection can identify relay coil failures, improving system reliability. The overcurrent protection prevents damage from relay coil short circuits. The device's 40V load voltage rating is sufficient for 12V and 24V relay coils. The PowerSO-20 package is compact, fitting into smart home control modules. The L9959's ability to drive inductive loads with built-in freewheeling diodes simplifies design. The wide operating temperature range allows installation in various locations within a home.
Recommended
Medical Device Actuator Control
In medical devices, the L9959 is used to control actuators such as pumps and valves. Its 8 channels allow precise control of multiple actuators, and the SPI interface provides reliable communication with the system controller. The low quiescent current is beneficial for battery-powered devices. The open-load detection ensures that actuators are properly connected, which is critical for patient safety. The overcurrent protection prevents damage from actuator faults. The device's wide operating temperature range allows use in various medical environments. The PowerSO-20 package is suitable for compact medical devices. The L9959's diagnostic features enable continuous monitoring of actuator health, reducing the risk of failure. The 40V load voltage rating is sufficient for most medical actuators, which typically operate at 12V or 24V.
Recommended
Recommended Products Summary
Engineering reference data for L9959 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | L9959TR | L9958 | MC33879 |
|---|---|---|---|---|
| Package | PowerSO-20 | PowerSO-20 | PowerSO-20 | PowerSO-20 |
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics | NXP Semiconductors |
| Number of Channels | 8 | 8 | 4 | 8 |
| Output Current per Channel | 1.2 A | 1.2 A | 1.2 A | 0.6 A |
| Supply Voltage (VCC) | 4.5V to 5.5V | 4.5V to 5.5V | 4.5V to 5.5V | 4.5V to 5.5V |
| Load Voltage | 40V | 40V | 40V | 40V |
| SPI Clock Speed | 5 MHz | 5 MHz | 2 MHz | 5 MHz |
| Quiescent Current | 10 µA | 10 µA | 10 µA | 20 µA |
Key Differentiators
- 8 channels in a single package (vs L9958)
- Higher SPI clock speed (vs L9958)
- Lower quiescent current (vs MC33879)
Design Notes
Ensure the VCC supply is decoupled with a 100 nF ceramic capacitor placed as close as possible to the VCC pin. Additionally, a 10 µF electrolytic capacitor is recommended for bulk decoupling. The load supply (up to 40V) should be decoupled with a 100 nF capacitor near the load connections to suppress transients.
The PowerSO-20 package has a thermal resistance of 35 °C/W. When driving all 8 channels at 1.2A each, the total power dissipation can be significant. For example, with a 0.5V dropout across each output, total dissipation is 4.8W, causing a temperature rise of 168°C above ambient. Use a solid copper area on the PCB and consider forced airflow for high-current applications.
For the SPI lines (CSN, SCLK, SDI, SDO), keep traces short and avoid routing near high-current outputs to prevent noise coupling. Use series resistors (e.g., 33Ω) on SPI lines to reduce ringing. The ground pins should be connected to a solid ground plane to handle the return currents from multiple outputs.
Compliance Information
RoHS compliant per STMicroelectronics product page. AEC-Q100 qualification not specified for this device.
